Eschenhagen 2 first designed a set of magnetographs in which this idea of small moment of inertia was carried to its useful limit, the magnets only weighing 1 .
The graphical methods of determining the moment of inertia of a plane system of particles with respect to any line in its plane may be briefly noticed.
The moment of inertia about any radius of the quadric (39) therefore varies inversely as the square of the length of this radius.
Single needles are never used, two being the least number, and these so arranged that the moment of inertia about every diameter of the card shall be the same.
It is usually accurate enough in deflection calculations to take for I the moment of inertia at the centre of the beam and to consider it constant for the length of the beam.
The fact that the moment of inertia of the magnet varies witli the temperature must, however, be taken into account.
The advantages of using small magnets, so that their moment of inertia may be small and hence they may be able to respond to rapid changes in the earth's field, were first insisted upon by E.
If the two materials are disposed symmetrically, the amount of load carried by each would be in direct proportion to the coefficient of elasticity and inversely as the moment of inertia of the cross section.